This invention relates generally to an improved tube cutter. More particularly, but not by way of limitation, this invention relates to an internal tube cutter to sever the tube using radial pressure on a tool bit applied against the tube wall as the cutter is rotated.
An example of prior art tube cutters includes a push type tube cutter, Model No. PIC 2000 manufactured by the Air Tool Division of Dresser Industries, Inc. Such a tool is manually operated. The operator manually pushes on a driver to activate the tool bit. Another example is a partially automatic tool bit feed internal tube cutter type KR68 offered by Kotthaus & Busch. It has a clutch which is manually inserted into a pawl by a holding lever and the feed is thus started. A threaded nut and cage arrangement push a mandrel forward to cause the pawl to move out of engagement with clutch dog 8 and against pins which in turn release a spring. The released spring pushes one end of a pivoted knife blade by means of a rod through the center of the tube cutter. The spring force thus pushes the knife or tool bit into the interior tube wall as it is rotated until the tube has been cut. To disengage the tube cutter, the threaded nut must be manually turned in the opposite direction by hand as far as it will go until all the blade is withdrawn and all the parts are returned to the starting position.
The prior art tube cutters have disadvantages including only partially automatic operation as the feed must be manually engaged and as disengagement requires manually unthreading a nut.
If the relative positioning between the pawl and the adjustment collar is not proper then the clutch will not disengage and the spring will not be released such that the tool will be driven by direct drive of the threaded nut thereby often causing tool breakage.
Other disadvantages may include uneven cutter pressure provided by the operator of a manual tool which may result in tool breakage. Also, after the tool bit completes its cut it must be manually disengaged.
One object of the present invention is to provide an automatic feed tube cutter which reduces or overcomes these and other disadvantages as will become more apparent in the description which follows.